Guide-roll arrangement for guiding relative movement of mast segments of a lift-truck and a lift-truck comprising a guide-roll arrangement

ABSTRACT

A guide-roll arrangement for guiding movement of a second mast segment relative a first mast segment of a lift-truck, comprising a roll pin having opposing first and second ends, wherein the first end comprises a recess, and a roll supported on the roll pin; and a sliding element arranged in the recess, said sliding element comprising opposing contact and sliding surfaces, wherein a support piece is arranged in the recess and comprising a contact surface for supporting the sliding element, wherein the contact surface of the sliding element is supported on the contact surface of the support piece and wherein one of the contact surfaces of the support piece and the sliding element is concave and the other is convex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Swedish PatentApplication No. 1551613-1 filed Dec. 9, 2015, the contents of which ishereby incorporated by reference as if set forth in its entirety herein.

TECHNICAL FIELD

The present disclosure relates to a guide-roll arrangement for guidingmovement of a second mast segment relative a first mast segment of alift-truck. The present disclosure also relates to a lift-truckcomprising a guide-roll arrangement.

BACKGROUND ART

Lift-trucks comprise various parts that are movable axially relativeeach other or with respect to the chassis of the truck. For example, anextendable mast of the lift-truck may comprise two or more mast segmentswhich are slidable arranged in each other so that the segments may bemoved apart and extended telescopically. The lift-truck may furthercomprise a movable carrier which supports components of the lift-truck.For example the lift-truck may comprise a carrier for supporting loadengagement means such as forks or clamping means. The carrier isarranged to be moved along a mast segment of the lifting mast of thelift-truck. A lift-truck comprising load engagement means in the form ofa lifting fork is typically denominated a forklift-truck. In so-calledreach lift-trucks, the mast of the lift-truck is attached to a carrier,i.e. a mast carriage, which is movable along an element of thelift-truck, for example along the support legs of the lift-truck oralong a U-beam in the support legs.

Typically, guide-rolls are provided to ensure a smooth axial movement ofone part relative the other part. For example, guide rolls may bearranged between a fixed mast segment and a movable mast segment of anextendable mast. The hub of a guide-roll is thereby attached to one ofthe mast segments whereby the roll itself engages one of the opposingsidewalls of a track which extends along the other mast segment. Acarrier for load engagement means may be provided with guide rolls whichrun in tracks on the inner mast segment of the lift-truck.

The guide-roll stabilizes the relative movement of the parts in theintended axial direction of movement since the surface of the guide rollis in contact with one of the opposing sidewalls of the track. However,to ensure a completely smooth relative movement between the parts it mayoften be necessary to prevent movement between the movable parts indirections which are non-parallel to the intended axial direction ofmovement. For this purpose, the guide roll may comprise a sliding blockwhich protrudes from the hub of the guide roll and is arranged to slidealong the bottom of the track. Examples of guide-rolls with slidingblocks for lift-trucks are disclosed in the documents WO2006024522, U.S.Pat. Nos. 4,234,057, 4,914,712, SE460116 and U.S. Pat. No. 4,375,247.

However, occasionally the tracks in which the guide-rolls run are notsufficiently straight, for example the bottom of the flanged track maybe uneven. It is also possible that external forces may displace one ofthe parts in relation to the other. This may cause the sliding block ofa conventional guide-roll to be pressed with an uneven pressure onto thebottom of the track. This is turn may result in uneven and sometimesexcessive wear of the sliding block.

Thus, it is an object of the present disclosure to provide an improvedguide-roll arrangement for guiding movement of second mast segmentrelative a first mast segment of a lift-truck, whereby said guide-rollarrangement solves or at least mitigates at least one of the problems ofthe prior-art. In particular, it is an object of the present disclosureto provide a guide-roll arrangement which has long service life. It isalso an object of the present disclosure to provide a lift-truckcomprising an improved guide-roll arrangement.

SUMMARY OF THE INVENTION

According to a first aspect of the present disclosure at least one ofthe aforementioned objects is met by a guide-roll arrangement 50 forguiding movement of a second mast segment 112, 113 of a lift-truck 100relative a first mast segment 111, 112, 113 of said lift-truck 100,wherein said first and second mast segments 111, 112, 113 comprises anelongated track 114 having a bottom 115 and opposing sidewalls 116, 117,wherein the guide-roll arrangement 50 comprises:

-   -   a roll pin 10 having opposing first and second ends 11, 12,        wherein the first end 11 comprises a recess 13; and a roll 20        supported on the roll pin 10; and a sliding element 30 arranged        in the recess 13, said sliding element 30 comprising opposing        contact and sliding surfaces 31, 32;    -   wherein the roll 20 is configured to engage one of the opposing        sidewalls 116, 117 of the track 114 and the sliding surface 32        of the sliding element 30 is configured to slidable engage the        bottom 115 of the track 114; and    -   wherein the second end 12 of the roll pin 10 is configured to be        attached to one of the first and second mast segments 111, 112,        113, and a support piece 40 arranged in the recess 13 of the        roll pin 10 and comprising a contact surface 41 for supporting        the sliding element 30, wherein the contact surface 31 of the        sliding element 30 is supported on the contact surface 41 of the        support piece 40 and wherein one of the contact surfaces 31, 41        of the support piece 40 and the sliding element 30 is concave        and the other of the contact surfaces 31, 41 of the support        piece 40 and the sliding element 30 is convex.

In the guide-roll arrangement according to the present disclosure, themating concave/convex contact surfaces of the sliding element and thesupport piece allows the sliding element to move freely in alldirections and by any suitable angle in the guide roll arrangement. Thesliding surface of the sliding block may thereby remain with constantpressure in contact with the bottom of the track regardless of anyangular displacement between the two relatively movable mast segments ofthe lift-truck. In operation, this reduces considerably the wear of thesliding element which in turn results in less downtime of the lift-truckdue to maintenance and reduced operational cost for the lift-truck.

A second aspect of the present disclosure is a lift-truck 100 comprisingan extendable mast 110 having at least a first and a second mast segment111, 112 wherein said second mast segment 112 is movable relative saidfirst mast segment 111, wherein said first and second mast segment 111,112, 113 respectively comprises an elongated track 114 having a bottom115 and opposing sidewalls 116, 117, and the lift-truck 100 comprises atleast a first guide-roll arrangement 50 according to the presentdisclosure.

Further alternatives and advantages of the present disclosure aredisclosed in the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A schematic side view drawing of a lift-truck according to thepresent disclosure.

FIG. 2: A schematic front view drawing of the mast of a lift-truckaccording to the present disclosure.

FIGS. 3a, 3b, 3c : Schematic cross-sectional drawings of the mast of alift-truck according to the present disclosure.

FIG. 4: A schematic side view drawing showing a guide-roll arrangementaccording to the present disclosure.

FIGS. 5a, 5b : A schematic drawing showing the functional principle ofthe guide-roll arrangement according to the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The guide-roll arrangement according to the present disclosure will nowbe described more fully hereinafter. The embodiments describedhereinafter are provided by way of example so that this disclosure willbe thorough and complete, and will fully convey the scope of the presentdisclosure to those persons skilled in the art. Same reference numbersrefer to same elements throughout the description.

FIG. 1 shows schematically a lift-truck 100 according to the presentdisclosure in side view. The lift-truck of FIG. 1 is a reach lift-truck.However, other lift-trucks are also contemplated with the scope of thepresent disclosure, for example stacker lift-trucks and order pickerlift-trucks.

The lift-truck 100 comprises a mainframe 105 which in its forwardportion extends into two forward support legs 101 carrying supportwheels 102. A drive wheel 103 is arranged in the rear of the mainframe105. In FIG. 1 only one of the support legs and the support wheels areshown. The mainframe 105 supports a chassis 106 in which an electricaldrive motor for propelling the drive wheel and a hydraulic system forproviding hydraulic power to movable parts on the lift-truck isaccommodated (the motor and the hydraulic system are not shown in FIG.1). The chassis 106 further comprises a driver's compartment 104,comprising a seat and controls for driving and controlling thelift-truck (not shown in FIG. 1). The lift-truck 100 further comprisesan extendable lifting mast 110. The lifting mast 110 shown in FIG. 1comprises three mast segments: a first outer mast segment 111, a secondmiddle mast segment 112 and a third inner mast segment 113.

FIG. 2 shows a front view of the lifting mast 110. Each mast segmentthereby comprises two vertical uprights of e.g. I-beam shape that areinterconnected by crossbars (not shown). The outer mast segment 111 issupported on the main frame 105 of the lift-truck. The middle mastsegment 112 is arranged within the outer mast segment 111 and isarranged movable relative the outer mast segment 111. The inner mastsegment 113 is arranged within the middle mast segment 112 and isarranged movable relative the middle mast segment 112. Actuation of therespective movable mast segments 112, 113 is performed by hydrauliclifting cylinders and lifting chains (not shown). The lifting mast 110may also comprise further mast segments, such a forth and a fifth mastsegment. It is also possible that the lifting mast 110 only comprises afirst and a second mast segment.

Returning to FIG. 1. The lift-truck further comprises a load carriage118, which is arranged movable in the inner mast segment 113 such thatthe load carriage 118 may be moved relative the inner mast segment 113in vertical direction upwards or downwards. Different load engagingmeans may be attached to the load carriage 118, for example a liftingfork or clamping means such as gripping arms that are arranged movabletowards each other for gripping and holding a load. In the lift-truck ofFIG. 1 a lifting fork is attached to the load carriage 118.

As described, the lift-truck 100 of FIG. 1 is a reach lift-truck, i.e. alift-truck having the capability of moving the lifting mast 110 parallelto the main frame 105 of the lift-truck. The outer mast segment 111 isthereby supported on a lifting mast carriage 130, which is arrangedmovable in the support legs 101 of the lift-truck such that the liftingmast may be moved relative the support legs 101 back and forth indirection from the rear of the lift-truck towards the support wheels102. However, the lifting mast 110 may also be directly supported on themain frame 105 of the lift-truck, i.e. the outer mast segment 111 of thelifting mast 110 may be firmly fixed to the mainframe 105 of thelift-truck.

The lift-truck further comprises guide-roll arrangements 50 that arearranged to guide movement of the various parts of the lift-truckdescribed above. Thus guide roll-arrangements 50 are arranged to guidemovement of the second, middle, mast segment 112 relative the first,outer, mast segment 111. Guide-roll arrangements 50 are further arrangedto guide movement of the third, inner, mast segment 113 relative thesecond, middle, mast segment 112 and vice versa. Guide-roll arrangements50 may further be arranged to guide movement of the load carriage 118relative the inner mast segment 113. Guide-roll arrangements 50 may alsobe arranged to guide movement of the lifting mast carriage 130 relativethe support legs 101 of the lift-truck.

The guide-roll arrangement 50 according to the present disclosure ishereinafter described in detail with reference to the movable mastsegments 111, 112, 113 of the lifting mast 110.

FIG. 3a is a view from above of the lifting mast 110 of FIG. 2 and showsthe mast segments 111, 112 and 113 of the lifting mast 110. The outermast segment 111 comprises two uprights 111.1 111.2. The middle mastsegment 112 comprises two uprights 112.1, 112.2 and the inner mastsegment 113 comprises two uprights 113.1, 113.2. A first and a secondguide-roll arrangement 50 are attached to the respective uprights 111.1and 111.2 of the outer mast segment 111 and a third and a fourthguide-roll arrangement 50 are attached to a respective upright 112.1,112.2 of the middle mast segment 112.

FIG. 3b is an enlarged cross-sectional view of the right side of thelifting mast of FIG. 3a and shows the right uprights 111.1, 112.1 and113.1 of the mast segments 111, 112, 113 in cross-section. It isappreciated that the left side uprights 111.2, 112.2, 113.2 areidentical to the right side uprights 111.1, 112.1, 113.1. Each of theuprights of the respective mast segments 111, 112, 113 comprises atleast one elongated track 114 having a bottom 115 and two opposingsidewalls 116, 117. The track 114 extends along the respective uprightof each mast segment in axial direction between the ends of the mastsegment. The elongated track 114 may thereby extend along the entireupright or along a portion thereof. Depending on the mast configuration,an upright may comprise one track 114 or two tracks 114. Thus, a firsttrack 114 may extend along a first side of an upright and a second track114 may extend along a second side of the same upright.

A guide-roll arrangement 50 is arranged between the outer mast segment111 and the middle mast segment 112 and between the middle mast segment112 and the inner mast segment 113. The guide-roll arrangement 50 isthereby attached to one mast segment, e.g. the upright 111.1 of theouter mast segment 111 such that its roll 20 engages one of the opposingsidewalls 116, 117 of the track 114 in the adjacent upright 112.1 of themiddle mast segment 112 and such that the sliding block 30 engages thebottom 115 of the track 114.

FIG. 3c is a view from below of the lifting mast 110 of FIG. 2 and showsthat the lifting mast 110 comprises further guide-roll arrangements 50arranged in inverted order with regards to the guide-roll arrangementsshown in FIG. 3a . Thus, a fifth and sixth guide-roll arrangements 50are attached to a respective upright 112.1, 112.2 of the middle mastsegment 112 such that their respective rolls 20 engages a track 114 onthe adjacent uprights 111.1 and 111.2 of the outer mast segment 112. Aseventh and eight guide-roll arrangement 50 are attached to a respectiveupright 113.1 and 113.2 of the inner mast segment 113 such that theirrespective rolls 20 engages an opposing sidewall 116, 117 of a track 114on an respective adjacent upright 112.1, 112.2 of the middle mastsegment 112.

FIG. 4 shows a guide-roll arrangement 50 according to the presentdisclosure in detail. The guide-roll arrangement comprises a roll pin10, also denominated hub, which forms the center of the guide-rollarrangement 50. The roll pin 10 is of rotational symmetriccross-section, typically of circular cross-section, and comprisesopposing first and second ends 11, 12. Thus, the first and the secondends 11, 12 faces away from each other. The roll pin 10 furthercomprises an envelope surface 21 which extends between the first andsecond ends 11, 12. A roll 20 is supported on the envelope surface 21 ofthe roll pin 10. The roll 20 is journaled by ball bearings in the rollpin 10 such that it may rotate around the roll pin (not shown in FIG. 4,but indicated in FIG. 3b ). The first end 11 of the roll-pin 10comprises a recess 13 which extends from the first end 11 towards thesecond end 12. The recess 13 is thereby arranged in the centre of theroll pin 10. The recess 13 may be cylindrical and has a bottom 17 and acircumferential wall 18. A sliding member 30 is arranged in the recess13 such that the sliding surface 32 of the sliding member extends out ofthe recess 13. The sliding block 32 is typically a solid piece of e.g.plastic, brass or graphite.

The second end 12 of the roll pin 10 is configured to be attached to anyof the mast segments 111, 112, 113 of the lift-truck. Attachment of thesecond end 12 of the roll pin 10 to a mast segment may be performed bywelding.

The roll 20 of the guide-roll arrangement 50 may be made of steel and isconfigured to engage one of the two opposing sidewalls 116, 117 of theelongated track 114 in the mast segment. The roll is configured toengage, i.e. be in rolling contact with, one of the opposing sidewalls116, 117 or the track 114. The diameter of the roll is therefore lessthan the distance between the two opposing sidewalls 116, 117 of thetrack 114. For example, when the roll engages one of the opposingsidewalls 116, 117 there is a small gap between the roll and the othersidewall, for example of 2-5 mm. The sliding block 30 is configured suchthat the sliding surface 32 may engage the bottom 115 of the track 114(see FIG. 3b ).

According to the disclosure, a support piece 40 is arranged in therecess 13. The support piece 40 is arranged on the bottom 17 of therecess and comprises a contact surface 41 for supporting the slidingelement 30. The contact surface 41 is thereby facing away from thebottom 17 of the recess. The sliding element 30 has a contact surface 31which is opposite the sliding surface 32. The sliding element 30 issupported onto the support piece 40 such that the contact surface 31 ofthe sliding element 30 is in contact with the contact surface 41 of thesupport piece. The sliding element is thereby freely movable, i.e.slidable, over the contact surface 41 of the support piece 40. Thus,there are no retaining elements or forces between the contact surfaces31, 41 of the support piece 40 and the sliding element 30.

Further according to the disclosure, one of the contact surfaces 31, 41of the sliding element 30 and the support element 40 is convex and theother of the contact surfaces 31, 41 is concave. Thus, as shown in FIG.5, the contact surface 41 of the support element 40 is concave and thecontact surface 31 of the sliding element 30 is convex. However, it ispossible to design the support element 40 and the sliding element 30such that the contact surface 41 of the support element 40 is convex andthe contact surface 31 of the sliding element 30 is concave.

The advantage of freely supporting a sliding element 30 having a convexcontact surface on concave support surface 41 of a support element 40 isillustrated in FIGS. 5a and 5 b.

In FIG. 5a the sliding element 30 is supported on the support piece 40and the sliding surface 32 of the sliding element 30 is engaging thebottom 115 of a track in outer mast segment 111 which is oriented in asubstantially straight vertical direction. The roll of the guide-rollelement and the opposing sidewalls of the track in the mast segment havebeen omitted for clarity.

In FIG. 5b , the outer mast segment 111 is subjected to an externalforce F which displaces the mast segment 111 from the straight verticalorientation of FIG. 5a . However, the convex contact surface 31 of thesliding element 30 slides freely over the concave contact surface 41 ofthe support piece 40 and the angular orientation of the sliding element30 follows thereby the angular deviation of the outer mast segment 111.The sliding surface 32 of the sliding element 30 therefore remains infull contact with the bottom 115 of the track along the mast segment111.

Returning to FIG. 4. Preferably, both the sliding element 30 and thesupport piece 40 are of circular cross-section and the contact surfaces31 and 41 of the respective sliding element 30 and the support piece 40are spherical. This is advantageous since the mating spherical surfacecontact surfaces 31 and 41 allows for free mobility of the slidingelement 30 in all directions around its centre axis. Preferably, thecontact surfaces 31, 41 of the sliding element 30 and the support piece40 have the same diameter.

Preferably, the contact surface 31 of the sliding element 30 is convexand the contact surface 41 of the support piece 40 is concave. Thisdesign allows for a stable movement of the contact surface 31 of thesliding element 30 over the contact surface 41 of the support piece 40and also for improved self-centering of the sliding element 30. Theconvex contact surface 31 of sliding element 30 is typically achieved bya rounded end of the sliding element 30. The concave contact surface 41of the support piece 40 is typically provided by a depression in thesupport piece.

The sliding element 30 is preferably dimensioned such that its outerdiameter is less than the inner diameter of the recess 13. The diameterof the sliding element 30 and the recess 13 are thereby dimensioned suchthat a predefined gap 22 is achieved between the outer surface of thesliding element 30 and the circumferential wall 18 of the recess 13. Thepurpose of the gap 22 is to control the degree of mobility of thesliding element and the dimension of the gap 22 is thereby selected independency of the construction of the lift-truck in question. Forexample, the gap may be 1-2 mm.

To further control the degree of mobility of the sliding element 30, anannular distance element 15 may be provided in the circumferential wall18 of the recess 13 for supporting the sliding element 30 in radialdirection Y. The annular distance element 15 is preferably of elasticmaterial, such as rubber, and arranged in an upper portion of the recess13. The annular distance element 15 is preferably of circularcross-section and attached to the circumferential wall 18 of recess 13such that it contacts the sliding element 30. For example, the annulardistance element is partially inserted into a groove 18 in thecircumferential wall of the recess 13. The annular distance element 15thereby retains the sliding element 30 within the recess 13 and ensuresfurther that the sliding element 30 does not press into thecircumferential wall 18 of the recess 13 when it slides over the bottomof the track. This could result in that the sliding element gets stuckin the circumferential wall 18 of the recess 13.

The guide-roll arrangement 50 may further comprise a bore 14, such as athreaded bore, extending from the second end 12 of the roll-pin 10 tothe recess 13. A threaded adjustment element 16, such as a threadedscrew or bolt, may be arranged trough the threaded bore and connected tothe support piece 40 to provide the possibility of moving the supportpiece 40 and thus the sliding element 30 in axial direction of theroll-pin (This allows for simple adjustment of the sliding element 30.

The radial direction Y and the axial direction X are indicated by arrowsin FIG. 4.

When in the present disclosure reference is made to a first mast segmentand a mast second segment this is made for illustrative purpose only. Itis appreciated that, for example, the middle mast segment may beconsidered a first mast segment and that the inner mast segment may beconsidered a second mast segment when the inner mast segment movesrelative the middle mast segment.

The invention claimed is:
 1. A guide-roll arrangement for guidingmovement of a second mast segment of a lift-truck relative to a firstmast segment of said lift-truck, wherein the first and second mastsegments respectively comprises an elongated track having a bottom andopposing sidewalls, wherein the guide-roll arrangement comprises: a rollpin having opposing first and second ends, wherein the first endcomprises a recess, a roll supported on the roll pin, and a slidingelement arranged in the recess, the sliding element having a contactsurface and an opposing sliding surface; wherein the roll is configuredto engage one of the opposing sidewalls of the track, wherein a portionof the sliding surface of the sliding element continuously contacts thebottom of the track as the sliding element translates along the track,wherein the second end of the roll pin is configured to be attached toone of the first and second mast segments, wherein a support piece isarranged in the recess of the roll pin and has a support piece contactsurface for supporting the sliding element, wherein the contact surfaceof the sliding element is supported on the support piece contactsurface, and allows for radial movement of the sliding element in therecess, and wherein one of the support piece contact surface and thecontact surface of the sliding element is concave and the other of thesupport piece contact surface and the contact surface of the slidingelement is convex.
 2. The guide-roll arrangement according to claim 1,wherein the sliding element and the support piece have circularcross-sections and the contact surface of the sliding element and thesupport piece contact surface are spherical.
 3. The guide-rollarrangement according to claim 1, wherein the contact surface of thesliding element is a rounded end of the sliding element and the supportpiece contact surface is a depression in the support piece.
 4. Theguide-roll arrangement according to claim 1, wherein the contact surfaceof the sliding element and the support piece contact surface havecorresponding diameters.
 5. The guide-roll arrangement according toclaim 1, wherein the recess comprises an annular distance element forsupporting the sliding element in radial direction (Y) of the recess. 6.The guide-roll arrangement according to claim 5, wherein the annulardistance element comprises elastic material and is configured to allowradial movement of the sliding element in the recess.
 7. The guide-rollarrangement according to claim 1, further comprising a threadedadjustment element extending through a threaded bore from the second endof the roll pin to the recess, wherein the threaded adjustment elementis connected to the support piece to move the support piece in axialdirection (X) of the roll pin.
 8. A lift-truck comprising an extendablemast having at least a first and a second mast segment wherein saidsecond mast segment is movable relative said first mast segment, whereinsaid first and second mast segments respectively comprise an elongatedtrack having a bottom and opposing sidewalls, and the lift-truckcomprises at least a first guide-roll arrangement according to claim 1.9. The lift-truck according to claim 8 wherein at least a first and asecond guide-roll arrangement are attached to the second mast segmentand wherein at least a third and a fourth guide-roll arrangement areattached to the first mast segment.
 10. The lift-truck according toclaim 8, comprising a third mast segment which is movable relative saidsecond mast segment.
 11. The lift-truck according to claim 10 wherein atleast a fifth and a sixth guide-roll arrangement are attached to thesecond mast segment and wherein at least a seventh and an eightguide-roll arrangement are attached to the third mast segment.
 12. Theguide-roll arrangement according to claim 1, wherein the sliding elementis configured to pivot relative to the support piece.
 13. The guide-rollarrangement according to claim 1, wherein the sliding surface of thesliding element is parallel to the bottom of the track.
 14. Theguide-roll arrangement according to claim 1, wherein the contact betweenthe sliding surface of the sliding element and the bottom of the trackgenerates a constant pressure.